Improvement in fluid-pressure-brake apparatus



G. WESTINGHOUSE, Jr. Fluid-Pressure Brake Apparatus.

No. 217.836. Patented July 22,1879.

NTED STATES PATENT FFICE.

GEORGE WESTINGHOUSE, JR., OF PITTSBURG, PENNSYLVANIA.

IMPROV-EMENT IN FLUlD-PRSSURE-BRAKE APPARATUS.

Speciiication forming part of Letters Patent No. 217,836, dated July 22, 1879; application filed May 28, 1879.

is an elevation thereof to a reduced scale; and

Fig. 3 is a detached sectional view, showing lthe devices in the reverse operation to that represented in Fig. 1.

My present invention relates to certain improyemen ts in railway tluidpressure-brake apparatus of the general type commonly known as the automatic, but instead of using an auxiliary reservoir under each ear, in combination with a brake-cylinder, I use what I term differential pistons and cylinder, or a cylinder fitted with pistons of ditferent areas subject to air-pressure, and on the same stem, in such manner that While the pistons are subject to air-pressure operating on both, the excess of aggregate pressure, acting on the larger piston, shall hold both pistons back, in which position the brakes will be off; but on the escape of air from in front of the larger piston, the pressure on the other piston will give both pistons a forward stroke, and so apply the brakes. This apparatus belongs more especially to that class known commonly as the automatic, in which while air-pressure is kept up the brakes zre off, but on the reduction of air-pressure in the brake-pipes the brakes are applied.

A cylinder of the kind referred to is represented atR. One end is made larger than the other, so that the piston P therein shall have an area subject to air-pressure somewhat greater than the other or smaller piston, P. Both pistons are packed as against the pressure, and both are secured on the same stem R', which latter has the usual or any required connection with the brake-levers. As a means of regulating or governing the application ot' air-pressure to these pistons, I make use of a device which in many respects resembles that described in United States PatentNo.172,064, granted to me Januar 711,1876; but for greater simplicity and convenience, as well as to secure greater durability, I prefer to make the valve-case in three parts, (designated generally as A, B, and 0,) the ends of G being seated in the adjacent faces of A and B, the joints packed by gaskets a' and b', and all secured together by screw-bolts a. 1

Connection is made with the brake-pipe by the branch A1, governed by a cock, A2, so as to cut the apparatus of any one car out of action in case ot' accident to any of its parts.

A cylindrical extension, A3, projects up around the piston-barrel b.

The central section, G, except as herein explained, is the same in mechanical structure and operation as the corresponding part in the patent above named, as also the piston C and valve D; but the stem c5 differs from the corresponding device in said patent in having a valveshaped shoulder at its upper end, which operates against a properly-shaped seat, as at s, in the lower face of the piston C.

The collar c? and spring 03 operate in the manner set forth in said patent, as also the extension c', except that the lower part of the latter, which fits the passage through the piston, and is so long that its upper end remains in such passage at the extreme endot the stroke of the piston, has a notch, Ii, in one side of it, which, when the piston is raised into the position shown in Fig. 3, allows the air-pressure to tiow from below the piston, through the passage, into the chamber above. The stem c4 carries a slide-valve, D, held down by a spring, d, and prevented from turning by a stud, d1, as in said patent.

The port E leads, by a pipe, E', to the larger or forward end of the brake-cylinder R, and the port F, by a like pipe,.F, to the opposite end. The port d3 leads from the interior airpassages to E, and the port d? leads to the external air. By a port, u, provision is made for admitting the compressed air to the under side of the piston C.

The operation is as follows: Air or other Huid pressure, being admitted at A1, acts on the under side of C, so as to bring the devices to the position shown in Fig. 3. The escapeport 0lz is then closed by the valve D, and the port d3 is open. Air-pressure then passes through the central passage in the piston C', and through pipes E and F', so as to charge both ends of the brake-cylinder; but the piston P being the larger, the excess of pressure thereon will force both pistons and their stem to the right, and the brakes will be off and the train in running order; but on a reduction of air-pressure in A1, the back-pressure of the air on the piston C will result in giving the piston a reverse stroke, so as to close the passage through it, and then bring all the devices to the position shown in Fig. l. The ports d2 and d will thus be brought into communication, and the pressure on the cylinder I will be released; but as the air-pressure still remains effective on P', both pistons and their stem will be forced to the left, and the brakes will thereby be brought into action.

Effective pressure in either direction may be varied at pleasure in the manner recited in said patent, or in the one to which it refers, and like changes and modifications can be made in this as in those; also, the brake-cylinder pistons may be reversed in their action, if so preferred; or, if aconsiderable difference be made in their areas, air-pressure through F may be introduced between them to force them one way, and a counterbalancing pressure through E to give a reverse stroke; also, the pistons P P may be inclosed in separate cylinders, if so preferred, but with such connections that in the manner describedthat is, being of different areas and air Aunder pressure beingalternately ap plied to and discharged from one-they shall (io-operate in giving the brakes the desired action, and for the purposes of the present case I use the term differential piston77 to designate this double arrangement of pistons of different areas.

The valve case or shell containing the devices for governing the application of the duidpressure is in effect a four-ported device-one port, A1, admitting air-pressure, two, E F, for applying the same, and one, d, for escaping. The piston, valve, and stem regulate the ow of fluid-pressure.

Instead of making the extension c' with the notch i, as described, it may be made round, with a sufficient reduction in diameter to allow the air to' pass, or it may have any irregular shape which will admit of the performance of the same function.

It will also be within my invention to subl stitute for the smaller piston a piston rod or stem so enlarged that it may perform the function of a piston, or vary to the desired extent the relative areas of the main piston, which, on its opposite sides, are subject to variations of air pressure under the conditions named, and the valve device described may ber advantageously used with such an arrange-A ment. Such an enlarged stem may in this connection, and within the purview ofthe claims hereinafter stated, be considered as the mechanical equivalent of the smaller piston, P.

I claim herein as my inventiony l. A differential piston, in combination with a four-ported valve-case, and suitable devices therein for directing the passage of fluid-pressure received through one of the ports through two of the others, whereby it shall be caused to act simultaneously in opposite directions on the differential piston, and also for directing such fluid-pressure at pleasure back from one of such two ports and out by the fourth, substantially as set forth.

2. The notched and reduced stern c1, in combination with ported piston C', substantially as set forth.

3. The arrangement of the escape-port d2 above the port 13in relation to the stroke of the valve D and piston C', whereby the charg ingstroke of the piston shall uncover d3, but close d2, but on the reverse stroke shall bring them into communication, substantially as set forth.

4. A valve-case made up of the part A, having a tubular extension, A3, and the part G, seated at one end in such tubular extension, and at its other end in the face of the third part, B, the whole being united by screw-bolts t a, substantially as described.

5. The valve end s of the stem e2, in combination with a valve-seat around the air-passage of the piston C', substantially as described.

Y In testimony whereof I have hereunto set my hand.

GEO. WESTINGHOUSE, JR.

Witnesses:

CHAs. BERKLEY HARRis,

17 Graceehm'eh Street, London. Jol-1N DEAN,

17 Gmcechurch Street, London. 

